Writing instrument



FIG. 1 is a front elevational view of the writing instrument showing my new design, the opposite side being identical thereto;

FIG. 2 is a right side elevational view thereof, the opposite side being identical thereto;

FIG. 3 is an exploded elevational view thereof showing the cap separated from the body;

FIG. 4 is a top plan view thereof;

FIG. 5 is a bottom plan view thereof; and

FIG. 6 is a top plan view thereof with the cap removed. 

The ornamental design for a writing instrument, substantially as shown and described. 